Raking classifier



arch 16, 1948. C.'H. SCOTT El AL BAKING CLASS IFIER Filed April 14, 1945 3 Sheets-Sheet 1 vm OW hv 11w 'LNTORSS CHARLES H. SCOTT a By FRANK L. GRANER,

ATTORNEY March 16, 1948. c. H. SCOTT El AL BAKING CLASSIFIER Filed April 14, 1945 s Shee tsSheet 2 INVENTORS.

s H. SCOTT CHARLE FRANK L. GRANER nub ATTORNEY March 16, 1948 c. H. 8cm Er AL 2,437,760

BAKING CLASSIFIER Filed April 14, 1945 3 Sheets-Sheet 3 INVENTORS' CHARLES :H. soon a BY FRANK L. GRANER,

ATTORNEY Patented Mar. 16, 1948 BAKING CLASSIFIER 7 Charles H. Scott, Summit, N.

J., and Frank L.

Graner, New York, N. Y., assignors to The Dorr Company, New Delaware York, N. Y., a corporation of Application April 14, 1945, Serial No. 588,360

18 Claims. 1

This invention relates to classifiers of the reciprocating rake type adapted to treat a bath of suspended solids for the purpose of fractionating the solids according to size so that an overflow contains suspended solids below a certain or predetermined size called fines, while the fraction of larger sized solids are progressively emerged and delivered from the classifier as sands. Such classifiers comprise a tank having an inclined bottom or deck along which longitudinally extending rake structures are adapted to have reciprocating strokes imparted to them.- During a stroke up along the inclined deck, settled solids are conveyed by the rakes. To that end the rake structures are lowermost and adjacent the deck during up-deck strokes and are uppermost and away from the deck during down-deck strokes. Thus, the rake structures are adapted to be raised and lowered during the transition between strokes. This invention revolves about (1) means for causing such alternate raising and lowering, and (2) means for causing such reciprocation.

Objects of this invention are to devise such means to be simple, cheap to build, dependable, efficient and yet substantially fool-proof. Other objects will appear as this description proceeds.

The features of advantage of the invention are derived from the use of this invention by embodying it in an arrangement wherein a shaft is longitudinally disposed in the classifier tank from which a balanced pair of rake structures is supported. Means are provided for imparting rocking rotational or oscillating strokes to the shaft under conditions whereby the shaft remains at rest for predetermined periods between strokes. The rake structures derive their support, at least in part, from this shaft so its rocking strokes raise and lower the rake structures alternately toward and away from the inclined decks. The rake structures derive support preferably from one or more cross- -arms, cross-bars, or transversely extending arms carried by the rockable shaft so that these arms rock unitarily with the shaft. Thus, the rocking shaft with the arms provide intermittently operating activating means for imparting in, alternation, raising and lowering strokes for moving the balanced pair of rake structures toward and away from the inclined deck of the classifier. There is a dwell or rest period between such strokes. Means are also provided for imparting reciprocating strokes to the pair of balanced rake structures in alternation. The means for rocking the arm-bearing shaft and the means for reciprocating the rake structures are so correlated that each rake struc- 2. ture moves up along the inclined deck when in lowered position with respect to its deck, and then down along its inclined deck when it is in raised position with respect to its deck. Between strokes or in the transition period between them, the rake structures are raised or lowered, as the case may be, by means of the intermittent rotational stroke of the shaft. Thus, while the rocking shaft raises and lowers the rake structures, the shaft also carries at least parts of the means for reciprocating the rake structures at times properly correlated with the raising and lowering motions.

The invention hereof may be embodied in various forms and modifications without departing from the spirit and scope thereof as will be manifest from the description which follows:

'As illustrative of one specific embodiment of the invention, reference is made to the accompanying drawings constituting a part of this specification and in which:

Fig. 1 is a vertical longitudinal sectional view of a classifier apparatus in which this invention has been embodied wherein the rake structure nearest the observer is in its forward or up-deck raking stroke and moves in the direction indicated by the solid arrows while a rake structure further from the observer is in its non-raking or down-deck stroke and moves in the direction indicated by the broken arrows.

Fig. 2 is a cross-sectional view taken as on the transverse plane indicatedby line 22 of Fig. 1 looking in the direction of the short arrows, to wit, towards the upper or sands-discharge end of the tank. 1

Fig. 3 is a cross sectional view taken as on a transverse plane indicated by line 33 of Fig. 1 looking in the direction of the arrows, to wit, towards the deep or overflow end of the tank.

Figs. 4 and 5 are respectively a partial elevational showing a detail of rake actuating mechanism applied to a side wall of the classifier tank.

Fig. 6 is a view of the nism shown in. Fig. 1 when an observer looks downwardly in the direction of arrow 6.

Fig. 7 is a partial perspective view of a form of mechanism for elfecting the various strokes for (1) raising and lowering the rakes, and (2) reciprocating the rakes. The view shows a central rockable shaft and a cross-arm carried thereby with means for operating these elements.

Figs. 8 to 11 inclusive are diagrammatic of motions of these elements and rest eriods or pivot that holds them to the shaft.

Fig. 12 is a further diagrammatic view shovving the relationships of strokes and rest periods of the various moving elements of-Fig.7. In order to facilitate understanding of the invention as to certain terminology employed herein it is here pointed out that (a) the deep or low end of the tank is the rear or liquid overflow end; (b) the upper or high end of the tank is the front or sands-dischargeend; (c) theportion of the tank at the right of a vertical plane which includes; a. centrally. located-imaginary line, extending from the rear. of vftheItank' forwardly to the front end thereof is considered hereinvassthe rightside portion of the tank. ,Thisfportion and each of.ce'r tainotherjparts or. structures .at the right. side ot-this plane are identified herein by the letter 'R, when'prece'din'g another identifying referencenumeral"orcharaeter; ,(d) that portion of the tank at, the, left of said centrally located plane as well sasaeach of; certain other parts o r structures at the 'le'ft'of said plane "areid'entified herein by ther'letter L when precedingfanother indicate the reciprocative v identifying. numeral or} character; (e) movement 4 of. a sands-raking strncture tpwams the sandsdischargefend of the tank-whengthe rake structure isinthe'Imvered po tion therefor is known as a forwardraking or rip-nec stroke; (1) movement of a sand-raking ;structure 1 in when the rake structureisdn its upper ost positionflra ised .awayjfroni th ifdeck'isi identified as a raised non-raking ordown-deck' strokey 1(a) up- I a direction v away fromthe sands-discharge endof thefdeck ward movement ftherake fstructurej fromja 7 lower up-deck rakingpositon to its raisedfn'onraking, position is id ti ie a fn ht lifted or front rising stroke: and ,(hij downward, movement of the rake structure from .rlaised non-raki'ng position to lower Iak lE-XPQSiF IIQiS identified as a rear lowered .or rear lowering stroke. In the drawings; t a a The. clas ifie l en A for feedin vl nd delivering solids suspension or mixturesuch as'metallurg'ical pulp containing suspended, s olids to be classified may be vide re a iable ec t pawith r spect to the tank. Such location is indicated by the arrow F.

The tank 1 t has i si'hhihgfhhtth or-inclined deck H .from which .ihere. riseside walls 3J2 and L12 and an endjw'all 14 in the'form of a bent plate having a lower section l5 extending at right angles to the inclined deck and. a veirticallyextending section It providing anjupper, overflow edge ll at elevationlower than that of theedge or flange portiohSRl3 and Lj- 3t,of the, side walls and lower thanthatof "the "forward .f 'ipper lend or edge 18 of. the inclinedjeek l l The overflow edge ll of theend'wall'serves asa weirl deterv mining thenorr'nal operative': overflow elevation for liquid withlusus pencled fine solids therein leaving the tank and thereby deterrnines the normal P 'QYB v eq RY UQ h l q i Wi h the n en verf qn .regeiv ie eund apr n vided at is from which liquid rid of heavy sus- ,resp ect' to pended solids passes from the tank to the place of disposition therefor. Raked or classified larger solids or sands pass as relatively dewatered solids from the forward upper end of the inclined deck. To impart rigidity to the tank there are angle members or edg -flanges providing the horizontal garde s @1 23? an ihrh e e fi periions at R29 and L20. In general the tank It] is made of sheet metal but it will be understood that it can 1 he madeof any suitable material depending upon ihere,,.ar fixedl ie e lon it d nal st ge transverse 'rakingrblades' s ch ;as 25, 25,. 21 2 8, tc-s h ableees x een evew lr re ns belowthe set oi longitudinals or stringers by .r ed.- i These, rake strnctures have; hangers or 'spifle'adi s sup o ng-r en pti n 'r vi d a b a riernplates lwfl andi BBQ L281 and L3u,,or strapsinal if prici- ,gii p t s th .upperpr f w rd magpie rake "s ictur'e are provided a s t compr ng pl tes e i na ed a R29. [,iidlflitfl'fibii the. ight ra e s c re. .112 and as L19 and' liliq, f r .the left jrake strucfiv re L2 A padin lm 'qrt nefs r is 1 3l videcl for the;l,0w'jend of rake structure R23 and acorresponding upporting strap L3! is provided fdr are anew; ma

Connection means. REZ Qand are ,tivelygp'rovided tween the right and left free '34 (carried by end or th 'rorwardjcrs-arm shaft 40 on, the one hand; and ,thefcorrespondi'ng carrieij fplates fififli and R30 pi- L29 s apes il -c me h re q neet am a R3 1 3. a e} e eee iv k p r siei be we n he .la

the typljeto which their; ent ly a rzl qalll r h i r lange- Fe t at-r v iep. b ex mple. is' in. th lo e e pos io :strncturef rigs; is in; it I raised pos t n and i moving in;its.;re arward or non raking direction V a i ialliyeri i 'a lv sp c d'r ti'onshipf. in re np ftq'ihei l qr or eck 1 the t n lheselbam iier eqan hean g aaiar d SQ-which. are? st rted r etp and, s ita ly supported t n n; o therefrorn' vvh r eby t Provide,

Tr d n -rocketed, v a so as to haverdckableforitiltable movement with fgi ti'l difiali axisgqrjthejshsnih members providing the cross-arms or cross-bars 34 and 35. As arranged with respect to the shaft, the structure thus provided has a semblance of a Lorraine cross, but in general the effective length of these cross-arms is the same. In other words, they are of equal length rather than of unequal length as is the case of the true Lorraine cross. In the construction shown, these cross-arms 34 and 35 have vertically extending pivotal mountings provided therefor. The crossarms are pivotally mounted at 4| on bearings 42 carried by the shaft and they extend to the right and left therefrom. They are capable of having imparted thereto reciprocative movement or strokes about pivot 4! whereby as the result of this pivotal movement, a lowered forward or updeck raking stroke is imparted to one rake structure, while a return raised down-deck stroke is imparted to the other rake structure.

At an end of each cross-arm 34 or 35, as the case may be, and between it and the carrier plates. R29 and R30 or L29 and'LSU or spreader supporting straps R3! or L3! corresponding thereto, there is provided a universal connection 46 embodying for example a spherical portion 41 on a rod section 48 extending from the cross-arm, and a socket member 49 carried from the spherical portion or section 41. The socket member 49 at the end of each arm constitutes a part of the connecting element or means extending from the free end of the arm to the corresponding carrier plates or straps. In other words, a socket member 49 constitutes part of each connecting means R32, L32, R33 and L33. The upper cross-arm 34 has an extension section 50 extending upwardly beyond the spherical portion 47 and this section 50 is cooperatively disposed with respect to a. surrounding telescoping member 5 I, the latter having a ball and socket connection with a traveling endless driving chain 52. This ball and socket connection is provided by a spherical knob or end member 53 integral with or connected to the telescopic member 5| and a traveling socket member 54 associated therewith, which socket member 54 is connected to the chain so as to move therewith.

The driving mechanism for the parts just referred to is supported by a fixed carrying bracket 55 secured to the outer portion of a side wall of the tank. This bracket in turn has or carries supporting bearings for the gear shafts hereinafter referred to. There is a supporting bearing 56 for drive shaft 51 which is actuated from any suitable source of power (not shown). The shaft 51 in turn carries and drives a spur gear or sprocket 58 of a set of such gears 58 and 59. The bracket carries a bearing for shaft 60 which serves as a support for the spur gear or sprocket 59. These gears are spaced apart along a line paralleling the sloping bottom of the tank and together provide support for the endless driving chain 52 which is actuated by the turning of the spur gear 58. The endless chain as thus mounted and driven provides upper and lower runs or sections BI and 63 paralleling the inclined deck of the tank and functioning according to the movement of the particular run to impart the forward or up-deck and the return or down-deck movements to the rake structures, to wit, whereby as one rake structure is moving forwardly in raking position at one period, the other rake structure is returning'in its non-raking position. The curved sections 62 and 64 of the chain function during the movement thereof to eifect the requisite raising and lowering strokes to the rake structures at the termination of and during the transition between the reciprocative strokes as the apparatus functions.

The mechanism justdescribed functions as fol lows: 1

When the traveling socket member 54 i being moved rearwardly along its straight upper path of travel 6 I, it imparts a forward or up-deck raking stroke to the right rake structure R123 which is lowermost and a reverse or return stroke to the left rake structure L23 which is raised. This is followed by the moving of the traveling socket member 54 downwardl along the rear curve or chain section '62 and this downward movement effects a lifting of the right rake structure R23 and a corresponding lowering of the left rake structure L23; then a continuation ofthe operation of the driving element effects amovement of the traveling socket member 54 forwardly along and with the lower run 63 of the endless chain thereby imparting a forward or up-deck raking movement for the left rake structure L23 and a corresponding down-deck or return movement of the raised right structure R23. By now, the traveling socket member has reached the end of its straight path of travel and there is'imparted thereto, by the forward curved section 64 of the chain as the latter continues to move,- that upward movement whereby there is effected a simultaneous lowering of the raised or right rake structure R23 and a simultaneous raising or lifting of the left rake structure L23 which has just performed a raking operation. In this way, continued movement of the chain effects the soughtfor reciprocative movements or strokes of rake structures during dwell periods in which there is no raising of the rake structure that is functioning to perform its raking operation.

Respecting the connecting means between the free ends of the cross-arm on the one'hand, and the carrier plates or supporting straps of the rake structures on the other hand, suitable sliding connections or lost motion means are provided whereby if an obstruction is encountered as a rake structure is lowered into or towards its raking position, such rake structure is not positively forced downwardly by the arm movement because of the lost motion means or sliding connection provided in and by the connecting means, for example, in the connecting means R32 and L32 the socket member 49 has slidablejengagement in a yoke 10 whereby it the rake structure in its downward movement encounters an; obstruction, the socket member 49 can continue to move downwardly within and along the yoke 10. Similarly, as to the connecting means R33 and L33 a. depending rod portion H has sliding engagement with an apertured upper section 12 of the yoke R3l or L31, as the case may be, whereby the rod can continue its downward movement with respect to the yoke if the rake structure which is supported by the particularyoke encounters an underlying obstruction.

I There will now be considered diagrammatic study views as presented by Figs. 7 to 11 inclusive. The purpose of these figures is to present in a simple manner fundamental features of an actuating mechanism of general application but useful particularly for imparting particular movement in timed relationship to corresponding balanced sets of structures or members in a serial or sequential manner but in different phase. Such a movement of the corresponding structures involves arrangements by which when one of the structures is raised, the other is lowered, and in which when one of the structures is moved in a forward reciprocative stroke, the other is moved inabackward reciprocative stroke and by which fixedly' secured was t DEW-3760 arrangement there is provided (-1) a 'dw'ell period between the raising and lowering operationshlhd 2) a dwell between reciprocative strokes of-the structures.

anrope'rative arrangement of a longitudinally ex- 15 tending 'memb'er in the form'ofan'oscillatable or 'rockable shaft carrying one for more transverse or cross-arm's mounted to rockuni't'a'iily with'th'e shaft to effect from the arms 'a's' thy rbckabbllt the aXis of the'shaft',j'a'ralisiiigbf thej'end'ofofie arm and thereby a portion 'orastrueturesupported therefrom, while there 'is' also effe'cted a lowering of the end "of'the other-arm andth'erby a portion of'the structure supp'orted therefrom.

The apparatus also includes means whereby there is effected a moving oflthe structurasupported from'theend of the -raised arm ina-backward or rearward direction and moving of the structure supported from the end of the other and lowered arm in a'forwarddirection, to wit,

during the period of dwell-between-raising and lowering movements of the endsofthe armsbecause of the rocking of the' cross arms about the axis of the rockable shaft.

- In Fig. 7'there is:indicatedthewockable shaft 40 just referred to. It is mounted=in suitable bearing members such-asat 38 and. Atrans- *ver'sely extending pivoted member or cross-earm The-cross-arm-fliis T I 40 run section BI and that thelcorresponding'start- 34 is mounted on this shaft.

pivotally mounted at 4| on a-bearing'42 carried on and by the shaft dfl. A cross-arm thus mohntediscapable of having a swinging or pivotal movement imparted thereto relative f to the rockable shaft" that 1 carries it, to wit; in 513181165 paralleling the longitudinal axis of Ethel-shaft.

Actuating means for the crossarm embodiesa sprocket and chain mechanism'suitablyisupported in bearings typified by al bear in'g SG -ln which hearing there is turnably mounted a driving s'haft 51 at one end of 'which'there is located a spur gear or sprocket- 58 's'ecuredto the shaft'swas'to' be driven thereby.

In another of similar stationarylbeai-ing; there is a shaft Bil carrying aspur gear or'sproeket' 59.

These sprockets are mounted "in spaced-relationship but so thata line through thea'ir-ial centers of the sprockets parallels-the-longitudinal aicis of .and carried by these sprockets"and is driven through the" medium of a shaft=driven "sprocket run sections f6! and 63"andeurved*eridruwsections 62 and 64. Itmoves inthedir'ectionindicated byfthettrrow: Orr this chaim 'therefls' "movetherewitha traveling socketmemberfi l for receiving the spherical ehd'53 of a teiescopingmemberm. -A"'rner'nber extending from the left end'Of thecrQssarm M embodies a' portion Ell-that entendsinto arid hastelescoping engageme'ntw'lththe member' S-Fas a result 'of' which'the trave1ing'"'socket memb'er is moved longitudinally along the straight-mustac- "tions fil M63, as thecase "possible what may be 'viewed'as a longitudinaf While the actuating mechanism of the-dia- 1 38 swingingmovementxoffthecross-warm.34 whereby therightiand :ieit endszthereof move in a general longitudinal spathzas indicated :by the straight line's T and' B ot-which T indicates the top path of the crossarm' when raisedand B indicates the bottom-path or the cross-arm when in lowered position, ior example, when the traveling socket nierii-b'er' fl" is moved by the-chain 'along the upper straight run-" fil the R'end'of the arm is moved forwardly along the lower or bottom longitudinal path B-and the-le'ftend of the arm is moved backwardly -or rearwardly along the upper or top path 'T.

When the traveling socket'i t is moved'by the 'chains along the curved run-62 the left end of thecross-armislowered-or-moved downwardly as indicated by the arc-shaped :heavy curve L and the right end of the arm is'raised or moved upwardly-along thepathas indicated by thearc- -When the' traveling socket member '54 is moved 'byth'echain'along thelower straight run63, the left end'of 'the'armis'moved forwardly-along the lower orbottom' longitudinal path B, while the 5 right end 'of .the arm is' moved backward or rearwardlyhlong the upper path T.

When the traveling socket member is moved by .the chain upwardly along the curved run 64, the .le'ftiend 'of the arm is raised or moved upwardly .as indicated by the arc-shaped curveL,

while the right end of 'the arm'isbeing moved 'downwar'dlyi'along a pathindicated by the arc- 's'hape'd curve R.

"-Thefourwst'ages or movements referred-to are successivelvillustrated;by therespective figures ing "point or position for the right and left ends .of thecross-arms :34 is indicated by the. lower starting positiont eat Rand thehigh-starting position Oat L, in Fig. 8.

Eor'the first stage movement (Fig. 8) the trav- '-te1ing-. socket member 54 moves forwardly in the direetion: indicated by-the arrow along the upper "run- 6 l with-.theconsequent movement of the .left "endtofthe arm'34 from O;to I,.to wit, along an 0 .upper gpathwayin a-backward or: rearward direc- :tion,-while1at the. same time the lower rend :of the *cross arm 3d moves inuawlowerforwardndirection from -o to I. .Tneipositionof:the tpartszznow is shown-in :Fig. 9.

5 1A5" toith'e :second: stage. of. movement ..('Eig. 9)

during-whichthett-raveling socketzmember moves :riow-nwardlyalongthe'curved run 62,-thereis ef- -;fected :a'-' lowering of. the :left end ofithe; arm: 34 rfiom the, point I'to the point IIrand ,aicorrespond- 4mg raising ofrtheiowrightend of:the;armjfr0m thjepoint -Irto' the point. II. These. movements are aiong-arc-shaped pathways indicatedabythe-broskenirline. Attheend ofzthis second stage the .parts anowoccupy the position: shown :in Fig. 10.

to the third stage (Fig? 10) the lowleft'end of the-armis-initsrearmost'position'andthe upper 'rig-ht end ofthearmis in its foremost or for- ''-war'd- -position. The movement of the traveling ---so'cket member-' along the straight lower run 62 effects-'a forward movement of the low left end of the-ami-Bfiirom the point II to the point III, to wit; in the forward longitudinal direction; while "the rightrend iif the arm moves from the point II of the point'in alongitudinalbackwardor rearward direction. The position shown in Fig. 11.

As to the fourth stage (Fig. 11) the traveling socket member 54 in moving upwardly along the curved run 64 to its original starting position 0, effects the movement of the left end of the arm from a low forward position, to wit, from III to O and the high right end of the arm moves downwardly from III to O, to wit, along a pathway indicated by the arc-shaped dashes until the parts assume the position shown in Fig. 8, at which time the four stages of operating movement are completed.

In connection with the foegoing, it will be observed that the up and down movements for the ends of the arm are attained from the interrupted or intermittent rocking of the cross-arm in an arcuate manner to the extent indicated by the angles formed by the cross-lines inthe fore part of Figs. 9 and 11, which lines indicate the limits of rocking movement through which the end of the arm is moved from low operative position to high inoperative position for members carried thereby and vice versa.

It will also be clear how the reoiprocative movement of the swinging arm 34 in a general longitudinal direction effects the longitudinal movements of the member supported from the arm when moved in a low forward direction and whereby such member is moved in a rearward direction when supported in an uppermost position therefor.

Fig. 12 is a more or less diagrammatic view of the chain and sprockets of Fig. 4, but in this case the path through which the chain moves has been divided into sections numbered A. B, C and D. A and C represent those periods when the rake structures are reciprocating-one raised and moving dowri deck, while the other is lowered and moving up-deck, meanwhile the rockable shaft and its cross-arms are at rest or in a period of dwell. B and D represent those periods when the rockable shaft and its cross-arms are rocking, downward during D and upward during B. during which the rake structures are at rest between their reciprocative strokes. or at least are in transition between such strokes.

Thus, the rockable shaft and its cross-arms comprise the activating means for imparting raising and lowering strokes to the rake structures, while the pivotal mounting of the cross-arms on the rockable shaft comprises activating means for imparting reciprocative strokes to the rake structures, It is to be noted that the rockable shaft and its cross-arm is the basic feature on which this invention is built, and also that the rake structures derive at least some of their support from the cross-arm, from which also the rake structures derive their reciprocative strokes. Means are also provided for automatically correlating these operations to be timed in their desired sequence and relationship.

We claim:

parts are now in the 1. A classifier having a tank with an inclined. bottom, a pair of laterally disposed rake struc-.

tures having transverse raking blades and longitudinally disposed in the tank, and means for imparting longitudinal reciprocating strokesto the rake structures including a rockable shaft longitudinally disposed With respect to the tank, means for supporting the rake structures from the shaft, and means for interruptedly rocking the shaft for alternately raising and lowering the rake structures during transition from one of their strokes to another. 7

2. A classifier according to claim 1, wherein the means for supporting the rake structures include cross-bars carried by the shaft and providing right and left arms extending outwardly from the shaft, and means for supporting one rake structure from corresponding arms of the cross-bars and the other rake structure from the other arms of the cross-bars.

3. A classifier according to claim 1, wherein the means for supporting the rake structures includes cross-bars carried by and movably mounted with respect to the rockable shaft, and the means for imparting reciprocating strokes to the rake structures includes members for transmitting such motion thereto to and through the medium of the cross-bars.

4. A classifier according to claim 1, wherein the means for supporting the rake structures includes cross-arms pivotally mounted on the rockable shaft.

5. A classifier according to claim 1, wherein the means for interruptedly rocking the shaft includes means for imparting to the shaft a rotational stroke in one direction and subsequently a rotational stroke in the opposite direction while leaving the shaft at rest between strokes.

6. A classifier according to claim 1, wherein the actuating means for interruptedly rocking the shaft includes sections for imparting to the shaft a rotational stroke in one direction and subsequently a rotational stroke in the opposite direction while leaving the shaft at rest between strokes; and wherein the sections for imparting reciprocating strokes to the rake structures include cross-arms carried by the shaft.

7. A classifier according to claim 1, wherein the means for imparting reciprocating strokes to the rake structures includes reciprocating arms for each rake structure carried by the rockable shaft and extending in opposite directions therefrom.

8. A classifier having a tank with an inclined floor sloping upwardly and forwardly from one end providing a pair f inclined decks. a pair of rake structures cooperatively disposed with a deck underlying each, means for raising and lowering each of said rake structures with respect to its deck, and means for moving each rake structure forwardly adjacent its deck when in lowered position and later for moving each rake structure rearwardly when in raised position; which said means comprise a main shaft extending longitudinally of the tank and overlying the decks, a first cross-bar mounted on the shaft providing arms extending laterally in opposite directions from the shaft, a second cross-bar spaced from the first mounted on the shaft providing arms extending laterally in opposite directions from the shaft, means connecting each arm on one side of the shaft with the same rake structure for supporting the latter, means providing functioning parts for interruptedly imparting limited rotational movement to the shaft and its cross-bars, and also providing operatively associated functioning parts for moving the rake structures reciprocatively.

9. A classifier according to claim 8, in which the means for imparting interruptedly rotational movement to the shaft coacts with at least one of said cross-bars.

10. A classifier according to claim 8, in which each cross-bar is pivotally mounted on the shaft to move about an upwardly extending axis, and means are provided for moving the cross-bars about such axis.

11. A;-classifier havinga tankzwith an= inclined bottom, a pair of riglrt andleftrake. structur s longitudinally disposedin the: tank; a-roclsable shaft, longitudinallydisposed with: respect tothe tank; meansfor supporting; said rake structures. from the shaft whereby'as the shaft is rockeddn one direction, it lowers the; right. rakestructure into low position for forward raking-movement and; raises. the left rake structure-in;1high-positionfor rearward non-raking. movement and whereby as; the shaft is: subsequently rocked. in the IGVGISegdll'ECtiO-II there. is-a lowering of; the left V-rakestructure into low-position'for forward raking movement and a raisingofthe-right rake structure into high position for rearward-nonraking movement; anactuating. meanshavin spaced-1y functioning sectins-f0r interruptedly imparting to said shaft'arocking. movement at one'period of time -inone direction andla.-subse-- quent period of time in an oppositedirection and also having spacedlyfunctioning'sectionsfor imparting between said-rockingperiods longitudinal movement to the respectiverake struc-- tures'but-in direction reversetoeach other, name? ly, the forward: raking movement to whichever rake structure is lowermost" and arearward-non; raking movement to whichever; rake structure is uppermost;-

12; A- classifier-having a ltankrwith. anl inclined bottom, a pair of-siderby-siddrake-structures longitudinally-disposed for functioning over the inclined bottom of which one sis; referred.-;to astheright rake structure: whilexthe otherrisxeferred to as the left. rakeistructure;:bearing means for supporting with-.respect: to: the tank a longitudinally extendingxrockable shaft; a tiltable: carrier and positioning mechanismuinclude: ing'; said shaft; transversely-extending; cr.oss arms: connected to and: rockable; with. the shaft providing right andi left-arm elements: extending outwardly in opposite directions from the shaft; and connectingelements betweenthe outen ends Qfsaid-arm elements andthe rakejstructures cor. responding thereto;- functionally-spaced-sections-forinterruptedlyim, partingto said'shaft arocking movement .at-one period of time in:adirectionfor raising, thezrig-ht structure while lowering theleft rake structure. and ate subsequent period of time in ardirectionfor-lowering-the left rake structure whileraising the right rake structure" and r alsohaving: functionally spaced-sectionsfor simultaneously" ima parting between i said rocking-1 periods longitudie nal movements to the rake structures in. directions reverseto each-other, namely, aforward rakingmovement to whichever.- rake structure is: lowermost and-a rearward nonerakingwmovement to the rake structure which is uppermost...

13; A classifier having a tankswfth-ansinclined floor sloping upwardly and forwardly-froma deep rear end-section" of the tankrtopavforward end section while providing a set of right and left longitudinallyextending;- inclined; decks; longs? tudinally extending; side-by-sidee, transversely spacedrakestructures'providing a set ofrightand left rake structures each-cooperativelydisposed. over theinclined deck towhich it corresponds; at lon itudinally-extending upwardly and forwardly inclined-shaft space between said rake structures;-,bearingsoperatively supported, with respect "tor-said tank wherein said shaftris rockably mounted .to have. tiltable movement" about its dongitudina-laxis; longitudinally spaced cross armsiz constituting: walking beams each tiltable with: and; bY?Sa1C1.

actuating; means--- having,

which in planoverlies the the-left. rake structure:

shaft Iandeachzprovidinga set ofright and left outwardly-extending arms; a means by which the rishtrakestructureis dependinglysupported from the outeriends' ofzthe right arms; means by which is dependingly supported from the outer-ends of :theleft arms; andactuatinggmeansahavingcoordinatingsections and parts constrnctedlandarrangedfor repetitively and in succession: carrying; out during a first, period a tilting-1 movement "of. the. shaft downwardly and torthafright'. for thereby lowering-the right rake structure while raising; the left rake structure, during a second period longitudinally moving the right rakastructure in a forwardralring direction' while; longitudinally moving: the left rake structure'in a'rearwardlnon-raking direction, during' a: third period tilting the shaft" downwardly andtotheleftfor -thereby loweringthe left rake structure while raising the right rake structure, and during; a fourthfperiod:longitudinally moving the lef-tfrake-structure inaforward direction while longitudinally moving the right rake structure in a rearward non-raking direction. I

14. A classifier having a tankwithan inclined .floor slopingupwardly'and.forwardly from'a deep rear; endof the tank:to a forward endlsection and providing: a-pai-r of longitudinallyextending laterally-disposed inclinedldeck sections respectively identifiable asan upward and=forwardly-extending rightdeck section and as anupwardly and forwardly-extending left'deck section; longitudi nally-extending laterally-disposed transverselyspaeed ,rakingstructuresofwhich. one is a right rake structure and the other a left rake structure eaclr of which-is-cooperatively disposed over the deck-l sectionrtoi which it: corresponds; a bearing member-which inlplan .v-iewis located between said rake structuresbut-which in-longitudinal vertlcal vlewdsdocatedat elevation higher than that of. correspondineiportions of said rake structures whenrtherlatter are inlthemid-vertical positions; a rockablemember mounted on saicfbearing member so as to. be carriedrby the latter-and providing aright arm-"and afleftarmeachextending laterally-"with respect to said bearing member; connecting, meansbetween theouter: end of the right arm and a portion ofnthe'might; rake structure for dependingly supporting a-portion ofithe latter from the outenend ofsaidright arm; connecting meanssbetween; the: outer. end of theleft arm and. aportion of the left rakestructure for dependingly-supporting aportionof the latter from the-outer end of saidleftarm;v and actuating means-having (ll asectlon-for imparting to said rockablamember a turningrmovement during a first period downwardly and to the right for simultaneously lowering the :right'rake structure while raising theleft lrake structure, (2) asection for movingithaloweredright rake structure forwardly while moving the -raised zleftralse structure rearward1y,dur1nga second period, ,(3) asectlon for imparting to said rockalole. member a turnin movement during a third'period downwardly and to the left for.slmultaneously l0wering.the left rake structurewhilexaising'theright rake structure; and (4); a;section' for moving'the lowered leftrake structure in'a forward direction while moving the raised-right rakestructure in a rearwarddirectionduring a fourth period; which said actuating means .as .awhole is constructed and arrangedlfor, effecting arepetitive. cycle .of the specified: operative movements for the raking structures.

15; Arclassifier havingratankwith an inclined floor sloping upwardly and forwardly from a deep l l 13 ee rear end section of the tank to a forward end section and providing a set of right and left longitudinally-extending inclined decks; longitudinally-extending side-by-side transversely spaced rake structures providing a set of right and a set of left rake structures each cooperatively disposed over the inclined deck to which it "corresponds; a longitudinally-extending upwardly and forwardly inclined shaft which in "plan overlies the space between said rake structures; bearings operatively supported with respect to said tank and in which said shaft is 'rockably mounted to have back-andforth rotational movement about its longitudinal axis; longitudinally-spaced cross-arms constituting walking beams each tiltable with and by said shaft and each providing a right and a left outwardly-extending arm; means by which each rake structure is dependingly supported from the outer ends of the arms corresponding thereto; means for actuating at one period the shaft for imparting a turning movement thereto downwardly and to the right for thereby lowering the right rake structure while raising the left rake structure; means for longitudinally moving at the next or second period the right rake structure in a forward raking direction while moving the left rake structure in a rearward non-raking direction; means for actuating at the next or third period the shaft for imparting a turning movement thereto downwardly and to the left for thereby lowering the left rake structure while raising the right rake structure; and means for longitudinally moving at the next or fourth period the lower left raking structure in a forward making direction while moving the upper right rake structure in a rearward non-raking direction.

16. A classifier having a tank with a deep rear end and a shallow forward end and an inclined bottom providing upwardlyand forwardly-extending right and left inclined deck portions; a pair of side-by-side but transversely-spaced longitudinally-extending right and longitudinallyextending left rake structures functionable whereby when one rake structure is in a low position for forward raking movement along the inclined deck portion to which it corresponds the other rake structure is in high position for rearward non-raking movement elevated from the inclined deck portion to which it corresponds; and rake-actuating means for imparting forward longitudinal raking movement for whichever rake structure is in low position therefor while imparting rearward longitudinal non-rakin movement to that rake structure which is in high position therefor; said classifier being characterized in that it also comprises a. rake-carrying and positioning means embodying a longitudinally-extending shaft, longitudinally-spaced bearings sup-ported with respect to the tank and in turn supporting said shaft whereby limited arcuate turning movements in opposite directions can be imparted thereto, longitudinally-spaced crossarms functioning as transversely-extending walking beams of which each cross-arm is connected to and moves with the shaft and provides a right arm and a left arm extending laterally outwardly from the shaft, connecting means between the outer ends of the right arms and the right rake structure whereby the latter is dependingly supported from the right arms, connecting means between the outer ends of the left arms and the left rake structure whereby the latter is dependingly supported from the left arms, and shaft-actuating means for rocking the shaft and cross-arms for thereby downwardly moving the high rake 1'4 structure to low raking position when said "lastmentioned; rake structure has substantially reached the end of its rearward non-raking movement and in a time spaced period thereafter for upwardly moving said last-mentioned rake structure to high position therefor when it has substantially reached the end of its forward raking movement; the parts constituting the rake actuating means and the parts constituting'the shaft rotating means being so constructed and arranged that during the normal operations thereof each rake structure has a period in'which it is lifted, a period in which it is longitudinally moved rearwardly in non-raking direction, a period in which it is lowered to raking position and a period in which it is longitudinally moved forwardly in low raking position.

17. A classifier having a tank with a deep rear end and a shallow forward end and an inclined bottom providing upwardlyand forwardly-extending right and left inclined deck portions; 9, pair of side-by-side but transversely-spaced longitudinally-extending right and left rake structures and functionable whereby when one rake structure is in a low position for forward raking movement alongtheinclined deck portiontowhich it corresponds the other rake structure is in high position for rearward non-raking movement elevated from and with respect to the inclined deck portion to which it corresponds; said classifier being characterized in that it also comprises a rakecarrying and positioning means embodying a longitudinally-extending shaft, longitudinallyspaced bearings supported with respect to the tank and in turn supporting said shaft whereby limited arcuate turning movements in opposite directions can be imparted thereto; longitudinally-spaced cross-arms of which each is connected to and moves with the shaft and provides a right arm and a left arm extending laterally outwardly from the shaft; connecting means between the outer ends of the right arms and the right rake structure whereby the latter is dependingly supported from the right arms, connecting means between the outer ends of the left arms and the left rake structure whereby the latter is dependingly supported from the left arms; and actuating means for repetitively carrying out the hereinafter specified return steps, said actuating means comprising (1) a rake-actuating section functioning during a first period for imparting forward longitudinal raking movement to whichever rake structure is in low position and for imparting rearward longitudinal non-raking movement for that rake structure which is in high position, (2) a shaft-rocking section functioning during a second period for tilting the shaft in a direction for raising the low rake structure when it has reached the end of its forward raking movement while simultaneously lowering the other rake structure into low raking position therefor, (3) a rake-actuating section functioning during a third period for imparting forward longitudinal raking movement to the last-mentioned rake structure while simultaneously imparting rearward longitudinal non-raking movement to the rake structure which is then in high position, and (4) a shaft-rocking section functioning during a fourth period for rocking the shaft in a direction for raising the low rake structure when it has reached the end of its forward raking movement while simultaneously lowering the other rake structure into low raking position preparatory to a repetition of the operating movements above outlined. 

